Previous studies of dental personnel have indicated that mercury exposure in the dental office represents a health hazard of dental practice. Attempts to measure the clinical health deficits associated with exposure have been few. Furthermore, the investigations that have been performed have been limited to evaluating current mercury exposure through blood, urine or hair analysis. The important relationship between cumulative mercury exposure and chronic health impairment has not been studied. This research proposal addresses itself to examining this relationship. The population consists of 300 dental auxiliaries who have had contact with mercury and a cohort of 50 dental auxiliaries who do not use mercury in their practice. Cumulative mercury levels will be ascertained by measuring bone and brain mercury levels in situ by an X-ray fluorescence technique that was developed in our laboratories. The top ten per cent of the ranked population will then be further examined for neurological and renal deficits. Electrodiagnostic studies will measure nerve conduction velocity, denervation, neuromuscular transmission and sensory actions potentials. Renal examination will include kidney urinary concentrating function, osmolality and urinary microprotein. The kidney mercury level will also be ascertained by X-ray fluorescence in the group demonstrating elevated bone mercury. Neuropsychological evaluation is being performed on the ranked upper and lower twenty-five percent of the population. A battery of eleven tests are being used. Current mercury exposure levels of these populations will also be determined through analysis of blood, urine and hair and correlated with total body mercury burden as determined by X-ray fluorescence. The results of these evaluations will indicate whether functional health deficits have occurred as a result of mercury accumulation.